1. Field of the Invention
The present invention relates generally to disk drives and more particularly to a method, apparatus, and computer readable program product for linearizing read/write head position error signals.
2. Description of the Related Art
Disk drives are magnetic recording devices used for the storage of information. The information is recorded on concentric tracks on either surface of one or more magnetic recording disks. The disks are rotatably mounted to a spin motor and information is accessed by means of read/write heads that are mounted to actuator arms which are rotated by a voice coil motor. The voice coil motor is excited with a current to rotate the actuator and move the heads. The read/write heads must be accurately aligned with the storage tracks on the disk to ensure proper reading and writing of information.
To accurately write and read data, it is desirable to maintain the head on the center of the track. To assist in controlling the position of the head, each sector of the disk typically contains a number of servo bits accurately located relative to the centerline of the track. The signals produced by the servo bits are typically demodulated into position offset signals which are used to determine the position of the head relative to the track, and to move the actuator arm if the head is not located on the track centerline.
Dual element transducers are increasingly utilized in hard disk drives because they are lighter than single element transducers. Dual element transducers include a single write element and a separate read element which is constructed from a magneto-resistive material. Such dual element transducers are commonly referred to as magneto-resistive (MR) heads.
Because of manufacturing tolerances, the separate magneto-resistive read element may be off-center from the write element of the head. Therefore, if data is written off the center of the track, to read the data, the servo system must move the head slightly off-center so that the read element is centered with the written data.
It also has been determined that the skew offset information for an MR head located over the inner tracks of a disk is different from that of an MR head located over the outer tracks of a disk. In addition, such MR head skew offset information is typically non-linear, and it also generally varies greatly between heads.
The present invention comprises a method, apparatus, and computer program product for linearizing a position error signal of a transducer in a hard disk drive. In one embodiment, a method includes providing a disk that includes a first plurality of tracks each having first and second servo bursts defining a track reference line of the respective tracks. A second plurality of the first plurality of tracks on the disk each includes third and fourth servo bursts defining a second plurality of different position offsets from the respective track reference lines, where the second plurality is no greater than the first plurality. The method further includes reading a second plurality of position error signals at the respective second plurality of different position offsets, positioning the read element of the transducer at the track reference line of a track, and obtaining a position error signal based on the predetermined offset, at least one of said second plurality of different position offsets, and at least one of said second plurality of position error signals. The method uses the position error signal to move the read element of the transducer to an off-reference line position for reading information.